Java Arrays合并排序算法的兑现

Java Arrays合并排序算法的实现

下面再来看看Arrays里面的合并排序算法实现。先把完整的源代码贴过来看看

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 private static void mergeSort(Object[] src,  Object[] dest,  int low,  int high,  int off) {int length = high - low;// Insertion sort on smallest arrays        if (length < INSERTIONSORT_THRESHOLD/*=7*/) {            for (int i=low; i<high; i++)                for (int j=i; j>low && ((Comparable) dest[j-1]).compareTo(dest[j])>0; j--)                    swap(dest, j, j-1);            return;        }        // Recursively sort halves of dest into src        int destLow  = low;        int destHigh = high;        low  += off;        high += off;        int mid = (low + high) >>> 1;        mergeSort(dest, src, low, mid, -off);        mergeSort(dest, src, mid, high, -off);        // If list is already sorted, just copy from src to dest.  This is an        // optimization that results in faster sorts for nearly ordered lists.        if (((Comparable)src[mid-1]).compareTo(src[mid]) <= 0) {            System.arraycopy(src, low, dest, destLow, length);            return;        }        // Merge sorted halves (now in src) into dest        for(int i = destLow, p = low, q = mid; i < destHigh; i++) {            if (q >= high || p < mid && ((Comparable)src[p]).compareTo(src[q])<=0)                dest[i] = src[p++];            else                dest[i] = src[q++];        }    }

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